Windows Vista took longer to arrive than hoped, and it might not have everything that was once planned, but Windows chief Jim Allchin maintains "It's a big deal."

And, more than five years after the debut of Windows XP, Vista is finally ready--at least, for businesses willing to buy at least five copies of the operating system. Those companies can get it starting Thursday, while consumers and those looking to get a Vista-equipped PC will have to wait until January.

For those who have been tuning out all the Vista chatter for the last few months, here's a primer on the new Windows. The update has security improvements, some snazzy new graphics and new desktop-searching abilities, among other features.

Large businesses can start getting Vista through volume-licensing contracts as of Thursday, while CompUSA is selling licenses to smaller businesses that purchase at least five copies of Vista. However, consumers and those looking to get new PCs with Vista installed will have to wait until the mainstream launch in January.

What if I buy a new PC now? Will it still run Vista? Microsoft is offering an "Express Upgrade" program that runs through early next year. It offers those who buy an XP machine now a free or discounted copy of Vista, once it starts shipping to consumers.

There's still the question of how Vista-ready the PC is. Microsoft is using two logos to help consumers get a sense of that. Some machines are billed as "Windows Vista Capable." A PC with that logo will be able to run Vista, but that sticker does not guarantee the computer will have enough graphics horsepower and other components needed to run all of the operating system's new features. Those who want to guarantee that should look for the shiny "Vista Premium Ready" logo.

So what's in this Vista thing?
Vista--which used to be called Longhorn--has evolved quite a bit since Microsoft first demonstrated an early version in 2003. The company has dropped plans to include its all-new WinFS file system. It has also changed the way it's implementing a new Web services architecture, known as Indigo, and a new graphics engine, dubbed Avalon.

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Business debut When do you think you will be running Vista at work?

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Among the key features of Vista as it currently stands are: security enhancements, a new searching mechanism, lots of new laptop features, parental controls and better home networking. There will also be visual changes, thanks to Avalon, ranging from shiny translucent windows to icons that are tiny representations of a document itself.

On the business side, Microsoft said Vista will be easier for companies to deploy on multiple PCs and that it will save costs by reducing the number of times computers will have to be rebooted.

Vista includes antispyware tools, Internet Explorer 7, an update to its Web browser, as well as Windows Media Player 11. It also has Windows Calendar, a new systemwide tool designed to do for datebook information what Outlook Express does for e-mail in Windows XP.

Is that all?
No. Among the other features Microsoft has publicly confirmed are: broad IPv6 support, improved clientside caching of data stored on a server, whole-volume encryption, a revamped synchronization engine, the ability to support laptops with an auxiliary display, automatic hard drive optimization and a secure boot-up process that helps prevent someone from gaining access to your data if your PC is lost or stolen.

Will my PC run Vista?
That depends on how recently you bought it and just how much Vista you want. To get the basics, like the new search abilities and improved security, you'll need a PC with 512MB of memory, an 800MHz processor and a 20GB hard drive with at least 15GB of free space. But to see Vista in all its glory, particularly its new Aero graphics, you'll really need a relatively modern video card with around 128MB of dedicated graphics memory or, for a system with shared systems and graphics memory, you'll need 1GB of memory.

Will it come in the same editions as in the past--Home, Professional, Tablet and Media Center? Microsoft announced in February that there will be six basic versions of Vista. On the consumer front, there will be a Vista Home Basic, which will lack Vista's advanced graphics or media features, and a Vista Home Premium, which will include such perks.

For businesses, there will be Vista Business as well as Vista Enterprise. The latter version will be available only to volume-licensing customers, and it will include extras like full-volume encryption and built-in Virtual PC software to run a second operating system as a virtual machine.

Vista Ultimate will put the best of the consumer and business features in one package. At the other end of the spectrum, a scaled-down Vista Starter edition will also be offered, though only on new PCs sold in emerging markets like India and Thailand.

How much will it cost?
Windows Vista Home Basic has a suggested price of $199 for the full product or $99 for those upgrading from a prior version of Windows. The higher-end Home Premium version is priced at $239 for the full version and $159 for those upgrading. Vista Business has a sticker price of $299 for the full version and $199 for the upgrade. The Ultimate edition carries a suggested price of $399 or $259 for the upgrade. Windows Vista Enterprise is available only to large businesses through volume licensing, with prices varying based on the number of licenses.

About the author

During her years at CNET News, Ina Fried has changed beats several times, changed genders once, and covered both of the Pirates of Silicon Valley. These days, most of her attention is focused on Microsoft. E-mail Ina.
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